LCD devices have several advantages and thus are generally adopted in the portable information products such as mobile phones, laptops, PDA, etc. However, conventional large-size LCD devices unavoidably suffer from the “flicker” problem, which becomes more serious with the size of LCD panel.
Generally, a LCD device has a LCD panel, wherein a gate driving circuit provides gate driving signals to turn on the TFTs on the scan line. Typically the gate driving signal is square-wave signal. However, parasitic capacitors/resistors on the scan line, resulting from the manufacture process, will result in RC delay and distort the waveform of the gate driving signal, as shown in FIG. 1A. The distortion becomes more serious when the gate driving signal goes to the rear parts of the scan line. Therefore the large-size LCD panel will need some solutions to this kind of flicker problem.
One conventional solution is to change the high and low reference voltage levels of the gate driving circuit so as to shift the highest level and the lowest level (VGH and VGL) of the gate driving signal and thus shape the gate driving signal. For example, as shown in FIG. 1B, U.S. Pat. No. 5,602,560 disclosed a LCD panel 1 with 1280×1024 pixels, which includes a data driving circuit 10, a gate driving circuit 12, and a compensation circuit 14. For a scan line S selected by the gate driving circuit 12, when the gate driving signal GS becomes OFF (low voltage level), the compensation circuit 14 will supply a compensation voltage CV, so as to shape the gate driving signal GS.
Conventional solutions to the flicker would require a variable voltage source. Although they can shape the gate driving signal, the variable voltage source will consume more power. Moreover, conventional solutions will make the circuit implementation complicated and increase the manufacture cost.
Therefore it is desired to have a novel LCD device adopting a simple, easy, and power saving way to shape the gate driving signal.